1. Technical Field of the Invention
The present invention relates to a method of transmitting data packets by radio within a local network comprising at least two slave communication units and a master communication unit through which all the data packets transmitted within the network travel. The present invention relates more particularly to such a method adapted to a configuration of the master unit according to which the latter comprises two processors interlinked by an internal interface.
2. Description of Related Art
It is known to use a star structure for the transmission of data within a network comprising at least three communication units. Such a structure is particularly adapted for networks comprising a reduced number of units communicating with one another. In such a network structure, one of the units plays a role of coordinator to which the other units are subservient. All the data intended to be transmitted between any two units of such a network are firstly received by the master unit which thereafter re-sends to one of the slave units the data initially intended for the master.
It is moreover often advantageous to distribute, within a communication unit, the functions executed by this unit between two processors interlinked by a connection internal to the unit.
The first processor can be especially adapted for the execution of a particular application. For this purpose, it can comprise means which are specifically appropriate for the execution of the program of this application, such as specified memory elements or a specified controller of interfaces for entering inputs and/or presenting data intended for a user of the unit.
The second processor executes so-called low level operations required for the transmission of data between this communication unit and an outside unit belonging to the network. In particular, it configures the data in a form adapted for their transmission, such as, in particular, a distributing of the data into packets adapted to the type of transmission used between the various communication units. It furthermore commands a sender/receiver of signals exchanged with the outside communication units.
Such a model of second processor operation may be common to all the communication units operating according to one and the same mode of transmission. This results in a reduction in the cost of the second processor, through a scale effect in the manufacture thereof. On the other hand, this second processor may be associated in one and the same unit with a first processor of variable model depending on the main application intended to be executed in this unit. A specialization of each communication unit is thus possible, while also benefitting from the cost reduction related to the second processor.
In what follows, we consider a distribution of the functions between the two processors of a communication unit according to which the application executed by the first processor manages the transmission of the data relating to this application within the network as a whole. In particular, the transmission of data between two slave units is controlled by the application itself, which fulfils a pivot function for retransmission of data intended for a slave unit, as a function of the recipient unit identified for these data. Such a role is commonly devolved to the application program residing in the master unit, because it alone is capable of interpreting all the data which pertain to the application and, consequently, of determining whether a processing needs to be applied to these data or whether the latter need to be retransmitted without modifications to one of the slave units.
All the data exchanged between any two units of the network are therefore transmitted to the first processor of the master unit via the connection, internal to this unit, between the two processors. As a result, the more considerable the amount of data exchanged within the network, the more appreciable is the energy consumption related to this internal transmission. In the case where the master unit possesses an autonomous power supply, of the cells or batteries type, its autonomy is then reduced on account of the internal transmission of a sizeable amount of data.
Another drawback of the transmission of a sizeable amount of data between the two processors of the master unit resides in the need to equip the internal connection for transmission between the two processors with a sufficient buffer memory. Apart from the cost of this buffer memory, the latter also gives rise to additional energy consumption.
There is accordingly a need to alleviate the aforesaid drawbacks.